Publicação
Utilização de dados geofísicos para identificação de estruturas arqueológicas e manchas de empréstimo de areia em meio marinho: Aquisição, processamento e interpretação de dados magnéticos e de sísmica de reflexão na área de Costa da Caparica
| Resumo: | Recently, climate change has led to an intensification of coastal erosion in Portugal, with consequences to its large coastal area with beautiful beaches that contribute to the tourist attraction and therefore to the growth of the economy. The lack of sand on the beaches is thus an increasing societal problem. The Operation Program for Sustainability and Resource Efficiency (POSEUR-02-1809-FC-000030, “Coastal Protection – Material Actions and Actions aimed at Knowledge production”) funded the CHIMERA project (“Characterization of lending spots on the continental shelf”, for artificial feeding of coastal stretches”) to investigate 4 potential areas for beach nourishment. This thesis is based on data obtained within the CHIMERA project. The main motivation behind this research is to mitigate the problem of coastal erosion in Portugal, by means such as artificial beach nourishment, essentially in coastal areas in critical erosion situation. Four areas have been identified by previous studies, and in this thesis project I concentrate my study on one of these areas, the Costa da Caparica (CC) area. Multidisciplinary geophysical methods were used to characterize the borrow sediments and to investigate archaeological objects that may interfere with and even prevent the dredging process of the borrow area. This research comprised the acquisition, processing and interpretation of Ultra-High Resolution Seismic (UHRS), magnetic data, hydrographic data, being the interpretation of these geophysical data complemented with sedimentological data. By the integration and cross-interpretation of these methods, the following aims were achieved: a) Definition of Seismo-stratigraphic models; b) Volumetric quantification and description of sediments; c) Determination of useful sediment and useful materials (medium to coarse sand); d) Seabottom morphology; I) Regional and residual magnetic anomaly II) Identification and location of remarkable magnetic / potential archeological structures. This thesis focuses essentially on the use of the magnetic and seismic method. The geophysical surveys lasted 60 days and were carried out on the IPMA research vessels RV DIplodus and RV Noruega. Total Magnetic Field (CMT) data was collected during the magnetic surveys, and subsequently corrected for diurnal variation, main magnetic field, denoise and leveling. Seismic profiles were acquired using a Sparker source of and a 24 -channel streamer. For processing magnetic data, Oasis montaj software was used, and RadexPro and Naviworks for seismic processing. Interpretation of the magnetic data allowed identifying one potential archaeological object. The regional and residual anomalies present two lineations parallel to NE-SW, NW-SE respectively, likely related to the intra-basement structure. Seven seismo-stratigraphic units were identified and mapped. The area has an unconsolidated sedimentary column of about 230.0 × 1063 where the maximum depth reached to the basement is 84.2 m. The computed volume of useful material for artificial nourishment is 6.49 × 1063. According to information obtained by seismics, hydrography and sedimentology, there is a good percentage of useful material, with higher concentration in the more onshore zone of the area. The area is located on the inner continental shelf and displays a monotonous seabed morphology punctuated by several depressions, where the sands of interest are located. |
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| Autores principais: | Almeida, Eveline Pereira |
| Assunto: | CHIMERA Costa da Caparica Arqueologia Magnética Marinha Sísmica de alta resolução Sismo-estratigrafia Anomalia Magnética Residual e Regional Teses de mestrado - 2019 |
| Ano: | 2019 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | português |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Recently, climate change has led to an intensification of coastal erosion in Portugal, with consequences to its large coastal area with beautiful beaches that contribute to the tourist attraction and therefore to the growth of the economy. The lack of sand on the beaches is thus an increasing societal problem. The Operation Program for Sustainability and Resource Efficiency (POSEUR-02-1809-FC-000030, “Coastal Protection – Material Actions and Actions aimed at Knowledge production”) funded the CHIMERA project (“Characterization of lending spots on the continental shelf”, for artificial feeding of coastal stretches”) to investigate 4 potential areas for beach nourishment. This thesis is based on data obtained within the CHIMERA project. The main motivation behind this research is to mitigate the problem of coastal erosion in Portugal, by means such as artificial beach nourishment, essentially in coastal areas in critical erosion situation. Four areas have been identified by previous studies, and in this thesis project I concentrate my study on one of these areas, the Costa da Caparica (CC) area. Multidisciplinary geophysical methods were used to characterize the borrow sediments and to investigate archaeological objects that may interfere with and even prevent the dredging process of the borrow area. This research comprised the acquisition, processing and interpretation of Ultra-High Resolution Seismic (UHRS), magnetic data, hydrographic data, being the interpretation of these geophysical data complemented with sedimentological data. By the integration and cross-interpretation of these methods, the following aims were achieved: a) Definition of Seismo-stratigraphic models; b) Volumetric quantification and description of sediments; c) Determination of useful sediment and useful materials (medium to coarse sand); d) Seabottom morphology; I) Regional and residual magnetic anomaly II) Identification and location of remarkable magnetic / potential archeological structures. This thesis focuses essentially on the use of the magnetic and seismic method. The geophysical surveys lasted 60 days and were carried out on the IPMA research vessels RV DIplodus and RV Noruega. Total Magnetic Field (CMT) data was collected during the magnetic surveys, and subsequently corrected for diurnal variation, main magnetic field, denoise and leveling. Seismic profiles were acquired using a Sparker source of and a 24 -channel streamer. For processing magnetic data, Oasis montaj software was used, and RadexPro and Naviworks for seismic processing. Interpretation of the magnetic data allowed identifying one potential archaeological object. The regional and residual anomalies present two lineations parallel to NE-SW, NW-SE respectively, likely related to the intra-basement structure. Seven seismo-stratigraphic units were identified and mapped. The area has an unconsolidated sedimentary column of about 230.0 × 1063 where the maximum depth reached to the basement is 84.2 m. The computed volume of useful material for artificial nourishment is 6.49 × 1063. According to information obtained by seismics, hydrography and sedimentology, there is a good percentage of useful material, with higher concentration in the more onshore zone of the area. The area is located on the inner continental shelf and displays a monotonous seabed morphology punctuated by several depressions, where the sands of interest are located. |
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